• Review an experiment and explain if it has been designed well
• Use randomized block design to create a hypothetical experiment to answer a research question

Well-Designed Experiment

The core purpose of conducting an experiment is to establish a cause-and-effect link between two distinct variables. Key elements within this process include:

• Independent Variable (Factor of Interest): This is the variable that we adjust to observe if it has an influence on another variable.
• Dependent Variable (Response Factor): This is the outcome variable that we believe is altered as a result of changes in the independent variable.

These components are fundamental in experimental research for tracing the effects of one variable on another.

independent and dependent variables

The independent variable is manipulated to observe its effect on the outcome, while the dependent variable is the outcome that is measured, reflecting the impact of the independent variable. Together, they are critical for discerning cause-and-effect in scientific studies.

In an experiment, the researcher manipulates values of the explanatory variable and measures the resulting changes in the response variable. The different values of the explanatory variable are called treatments. 

Treatments are experimental conditions into which the participants are divided, some into the a group receiving the treatment of interest and others into a control group that does not receive the treatment (a placebo). 

A placebo is a harmless version of the treatment that does not contain any active ingredients (e.g., a sugar pill). The placebo will typically look, taste, and smell like the treatment of interest or mimic it so that the two treatments appear identical to the subjects; this way the subjects don’t know which they are receiving.

treatments and placebos

Treatments are experimental conditions into which the participants are divided, some into the group receiving the treatment of interest and others into a control group that does not receive the treatment (a placebo).

 

A placebo is a harmless version of the treatment that does not contain any active ingredients (e.g., a sugar pill).

The single object or individual to be measured in the experiment is called an experimental unit. The experimental units of the whole experiment are split into two groups—one group receives the treatment of interest (this is usually called the experimental group) and the other group does not. The group that does not receive the treatment of interest or the placebo is the control group.

Experimental Group versus Control Group

The experimental group is the group which receives the treatment of interest.

The control group does not receive the treatment of interest.